Ultrasonic Hair Dryer

ABSTRACT

A device for drying hair includes a housing having an air inlet and an air outlet spaced from the air inlet to define an airflow path through the housing. The device also includes a fan disposed within the housing along the airflow path, a hairstyling implement disposed at the air outlet, and an ultrasonic transducer configured to generate ultrasonic vibrations. The transducer is coupled to the hairstyling implement to transmit the ultrasonic vibrations to the hair.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application entitled “Ultrasonic Hair Dryer,” filed Nov. 25, 2009, and assigned Ser. No. 61/264,287, the entire disclosure of which is hereby expressly incorporated by reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure is generally directed to hairstyling devices, and more particularly to hair dryers.

2. Description of Related Art

Traditional techniques for drying and styling hair involve the application of heat. Attempts to dry and style hair faster or create more robust holds have been based on increasing the amount of heat or airflow applied to the hair. The heat acts upon water molecules contained in the center of the hair. Restructuring the hydrogen bonds between the water molecules allows the hair to retain the desired styling.

Unfortunately, elevated amounts of applied heat tend to dry and damage hair, rendering the hair difficult to style, reducing shine, and ultimately resulting in unhealthy hair. Excessive heat can damage the outer layers of the hair, i.e., the cuticle, resulting in split ends. The hair becomes more limp and unable to hold desired styling, once the cuticle and inner shaft of the hair lose the water content that would otherwise provide strength.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a device for drying hair includes a housing having an air inlet and an air outlet spaced from the air inlet to define an airflow path through the housing, a fan disposed within the housing along the airflow path, a hairstyling implement disposed at the air outlet, and an ultrasonic transducer configured to generate ultrasonic vibrations and coupled to the hairstyling implement to transmit the ultrasonic vibrations to the hair.

In some cases, the ultrasonic transducer is disposed within the housing. Alternatively, the ultrasonic transducer is disposed within the hairstyling implement. Alternatively or additionally, the hairstyling implement is detachably coupled to the housing.

The hairstyling implement may be configured as a diffuser. Alternatively or additionally, the hairstyling implement includes a plurality of tines. Adjacent tines of the plurality of tines may then be spaced from one another in accordance with a wavelength of the ultrasonic vibrations. Alternatively or additionally, each tine of the plurality of tines may then have a length in accordance with a wavelength of the ultrasonic vibrations.

The hairstyling implement may have a length of about an integer multiple of a wavelength of the ultrasonic vibrations. Alternatively or additionally, the ultrasonic transducer includes a piezoelectric material to generate the ultrasonic vibrations. The hairstyling implement may then be made of a material having an acoustic impedance at about a midpoint between an acoustic impedance of the piezoelectric material and an acoustic impedance of the hair.

In accordance with another aspect of the disclosure, a device for drying hair includes a housing having an air inlet and an air outlet spaced from the air inlet to define an airflow path through the housing, a fan disposed within the housing along the airflow path, and an ultrasonic vibration assembly including a first component comprising a piezoelectric material to generate ultrasonic vibrations and further including a second component coupled to the first component and disposed at the air outlet. The second component includes a horn material having an acoustic impedance at about a midpoint between an acoustic impedance of the piezoelectric material and an acoustic impedance of the hair to transmit the ultrasonic vibrations to the hair.

In some cases, the second component is configured as a hairstyling implement. Alternatively or additionally, the device further includes a third component coupled to the first component by the second component. The third component may then be configured as a hairstyling implement. The third component may be made of a material having an acoustic impedance about equal to the acoustic impedance of the hair. Alternatively or additionally, the second and third components are constructed of a common material.

The first component may be disposed within the housing. Alternatively, the first component is disposed within the second component. Alternatively or additionally, the second component is detachably coupled to the housing.

The second component may be configured as a diffuser. Alternatively or additionally, the second component includes a plurality of tines. Adjacent tines of the plurality of tines may then be spaced from one another in accordance with a wavelength of the ultrasonic vibrations. Each tine of the plurality of tines may then have a length in accordance with a wavelength of the ultrasonic vibrations.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features, and advantages of the present invention will become apparent upon reading the following description in conjunction with the drawing figures, in which like reference numerals identify like elements in the figures.

FIG. 1 is a schematic view of an exemplary hair dryer constructed in accordance with one or more aspects of the disclosure.

FIG. 2 is a schematic, exploded view of an ultrasonic vibration assembly of the hair dryer of FIG. 1 to depict vibration generation and transmission components thereof in greater detail, including an ultrasonic transducer and a hairstyling or hairdressing implement configured as an attachment for the hair dryer.

FIG. 3 is a perspective, exploded view of another exemplary hair dryer having an alternative ultrasonic vibration assembly constructed in accordance with one or more aspects of the disclosure.

FIG. 4 is a perspective view of yet another alternative ultrasonic vibration assembly configured as an attachment for a hair dryer.

FIG. 5 is a perspective view of an exemplary diffuser constructed in accordance with one or more aspects of the disclosure.

FIG. 6 is a perspective view of an exemplary ultrasonic transducer of the diffuser of FIG. 5.

FIGS. 7 and 8 are perspective views of further exemplary diffusers constructed in accordance with alternative embodiments.

FIG. 9 is a perspective view of an exemplary ultrasonic transducer of the diffusers of FIGS. 7 and 8.

FIG. 10 is a perspective view of an alternative ultrasonic transducer suitable for use with the diffusers of FIGS. 7 and 8.

FIGS. 11 and 12 are schematic diagrams of exemplary drive circuits for controlling the operation of the ultrasonic transducers of the disclosed hair dryers.

FIG. 13 is a graphical diagram of data collected during energy transmission testing of the disclosed hair dryers.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure is generally directed to ultrasonic hairstyling devices that transmit ultrasonic vibrations to the hair to reduce the amount of heat applied for drying and styling. The ultrasonic vibrations generated by the disclosed devices generally improve hairdressing and hairstyling by decreasing the duration and, thus, the amount, of the applied heat, thereby improving the overall health of the hair, increasing shine, and improving styling hold. In this way, users of the disclosed devices can dry and style hair faster and create longer-lasting holds without having to resort to the application of more heat.

The disclosed hairstyling devices are generally configured as hair dryers or other devices that direct heated or unheated air to the hair for wet-to-dry styling. The energy carried by the ultrasonic vibrations is generally transferred to the hair via a hairstyling implement configured for contact with the hair. The energy from the ultrasonic vibrations then adds to the energy applied by the airflow such that the total energy reaches a level appropriate for drying and styling. The energy from the ultrasonic vibrations may also result in improved and more uniform heat distribution in the hairstyling implements, as well as within the hair itself. For these and other reasons, the application of the ultrasonic energy may lead to faster drying and less time needed to achieve and set a desired styling. With lowered amounts of applied heat, the likelihood or risk of damage to the hair decreases.

The hairstyling implements of the disclosed devices may vary considerably in form and function. The implements are generally disposed at an air outlet of the hair dryer. In some cases, the implement may be an optional attachment for the hair dryer. The implement may be configured as a diffuser, a concentrator, a comb, a brush, or any other hairstyling tool or instrument. Thus, in some cases, the implement may include a set of tines or teeth, which may be dimensioned in accordance with a wavelength of the ultrasonic vibrations. For example, the spacing between adjacent tines, as well as the length of the tines, may be selected to establish constructive interference for efficient transmission of the ultrasonic vibrations. In some cases, the implement may carry an ultrasonic transducer that generates the vibrations, including those cases in which the implement is detachable.

The hairstyling implements disclosed herein may also be constructed with one or more materials that promote the efficient transmission of the ultrasonic vibrations to the hair. To that end, the hairstyling implement may be made of a material having an acoustic impedance that matches an acoustic impedance of the hair (or that is otherwise well suited for transmission to the hair). In these and other cases, the overall assembly of components that carry the ultrasonic vibrations may include a component, e.g., a horn (or section thereof), constructed of a material having an acoustic impedance at about a midpoint in the range between an acoustic impedance of the piezoelectric material used to generate the vibrations and the acoustic impedance of the hair.

Although described below in connection with hair dryers, the ultrasonic vibrations may be useful in connection with a variety of hairstyling tools, instruments, and techniques. Thus, the disclosed hairstyling devices are not limited to hair dryers. In some cases, the ultrasonic vibrations may be transferred while the hair is clamped, clipped, or otherwise in contact with styling tools or instruments. Clamping or clipping is only one of a variety of ways in which contact between the vibrating elements of the disclosed devices and the hair may be ensured.

Turning to the drawing figures, FIG. 1 depicts a hair dryer 20 having a housing 22 and a handle 24 from which the housing 22 extends, and which may be integrally formed with the housing 22 to any desired extent. The housing 22 has a main body 26 from which the handle 24 extends, and a barrel 28 extending forward from the main body 26. The housing 22 has an air inlet or intake 30 and an air outlet or exhaust 32 that generally define an airflow path of the hair dryer 20. The air inlet 30 may be disposed at a rearward end of the main body 26, and the air outlet 32 may be disposed at a forward end of the barrel 28. The airflow path extends along a longitudinal axis of the barrel 28 along which the air inlet 30 and the air outlet 32 are disposed. One or more fans 34 and one or more heating coils (or other elements) 36 are disposed along the airflow path to heat the air as it is forced through the air outlet 32. The fan(s) 24 and the heating coil(s) 36 may be enclosed within the main body 26, the barrel 28, or both. Indeed, any number of fans and heating elements may be disposed within the main body 26 and the barrel 28 at a variety of locations, including those near the forward end of the barrel 28.

These components of the hair dryer 20 may vary considerably from the schematically depicted example shown in FIG. 1. The housing 22 generally, as well as the handle 24, the main body 26, and the barrel 28, may be shaped, sized, and oriented in a wide variety of ways. The ultrasonic features of the disclosed hairstyling devices are well suited for use with a variety of different configurations and constructions. For instance, the handle 24 need not extend perpendicularly from the longitudinal axis of the main body 26 and the barrel 28 as shown. The airflow path may also vary, and need not begin at one end of the main body 26 or otherwise pass through the main body 26 as shown. The heating coils 36 need not be oriented lengthwise as shown, and instead may be oriented, for instance, radially (e.g., in one or more planes transverse to the longitudinal axis).

The components of the housing 22 may be integrally formed to any desired extent. For example, the handle 24, the main body 26, and the barrel 28 (or any subset thereof) may be constructed as a two-piece shell. To that end, one or more of these components may be constructed from a pair of molded, half-cylinder plastic covers secured to one another via snap-fit connectors, screws, or other fasteners. These and other parts of the housing 22 may be constructed of a variety of materials other than plastics, including stainless steel. The handle 24 may include a rubberized, plastic, or other grip surface (not shown), which may be configured as a sleeve or other covering. In alternative cases, one or more of the handle 24, the main body 26, and the barrel 28 are discrete structures connected to one another via one or more fasteners (e.g., one or more snap-fit connectors) or some other coupling mechanism.

The handle 24 is configured as a hollow tube to accommodate a number of user interface or control elements, such as electrical components and circuitry. These components generally direct and support the operation of the hair dryer 20, which includes an ultrasonic vibration feature as described below. In this example, the handle 24 houses a circuit board 38 coupled to the fan 34, the heating coils 36, and an ultrasonic transducer 40 for control thereof.

One potential advantage of the disclosed hair styling devices is that the number, size, or intensity of the heating coils 36 may be reduced as a result of the application of ultrasonic vibrations, as described below. Nonetheless, the hair dryer 20 may still have a conventional amount of heating capacity to provide the operator with various operational options, including a non-ultrasonic option. To that end, the hair dryer 20 may include one or more user interface elements 42 (e.g., switches and the like) to select an operational configuration or control the operation thereof. In these and other ways, the hair dryer 20, for instance, may be configured to present a range of possible heating levels to the operator to accommodate different hairstyling requirements arising from, for instance, differing hair thickness. The circuit board 38 may include a number of integrated circuit (IC) chips 44 and other circuit elements responsive to the user interface elements 42 to direct power from a power cord 46 to the heating coils 36, the ultrasonic transducer 40, and other electrical components of the hair dryer 20. To that end, the hair dryer 20 also includes a number of wire pairs 48 running from the circuit board 38 to the other functional components of the hair dryer 20.

The circuitry responsible for controlling the heating and ultrasonic vibrating functions may be integrated to any desired extent. In some cases, a separate circuit board may be disposed within the housing 22 to handle one of the two functions alone. In any event, the circuit elements 44 may be disposed in a location within the housing 22 (e.g., within the handle 24) to avoid the heat generated by the heating coils 36. Because one or more of the circuit elements 44 may also constitute sources of heat, the circuit elements 44 may be nonetheless configured for operation in an elevated temperature environment. Temperature levels within the housing 22 may exceed normal operating temperatures even though the circuit elements 44 are spaced from the heating coils 36. To help dissipate heat, one or more of the circuit elements 44 may include a heat sink 50. In some cases, the hair dryer 20 may include a barrier, divider, wall, or other structure (not shown) within the housing 22 to block the transmission of heat from the main body 26 and the barrel 28 to the components within the handle 24.

One or more of the user interface control elements 42 may be directed to activating and deactivating the hair dryer 20 or one or more operational features thereof, including ultrasonic vibration. Other control elements 42 may be directed to selecting or determining operational parameters, such as heat level, air flow rate, and ultrasonic vibration intensity. For instance, an operator may be given an opportunity to adjust the heat level to a lower temperature when the ultrasonic vibration feature is activated. In other cases, the heat level is automatically reduced upon activation of the ultrasonic vibration feature. More generally, an operator may adjust the temperature level, air flow rate, etc., to customize the hair dryer 20 for personal use requirements or preferences.

The positioning, mounting, and other structural and electrical characteristics of the electrical and circuit-related components of the hair dryer 20 may vary considerably. For example, circuit elements may be disposed on more than one circuit board or otherwise spaced apart to improve heat dissipation. Details regarding the electrical characteristics of the circuit-related components are provided below in accordance with multiple embodiments.

As described below, the ultrasonic transducer 40 is generally configured to generate ultrasonic vibrations to improve and facilitate hairstyling through lower levels of applied heat. In this example, the ultrasonic transducer 40 is a part of an ultrasonic vibration assembly 51 having components disposed both within and external to the barrel 28. More specifically, the transducer 40 is located within the barrel 28, mounted and held radially stationary therein. In that way, the vibrations generated by the transducer 40 are transmitted from within the barrel 28 to a location in front of the air outlet 32, at which point the vibrations are, in turn, transmitted to the hair in contact therewith. To that end, the ultrasonic transducer 40 is generally disposed in a position that allows the vibrations to be transmitted to a styling implement 52 configured for contact with the hair being styled. In this example, the transducer 40 is mounted or oriented lengthwise along the longitudinal axis of the barrel 28 at or near the air outlet 32. The transducer 40 may be secured to the barrel 28 via one or more mounting posts or braces 54 that couple the transducer 40 to inner walls of the barrel 28 in a manner that does not significantly dampen or otherwise misdirect the ultrasonic vibrations. However, the characteristics of the mounting structure may vary considerably from the example shown, and may include other types of mounting hardware (e.g., brackets, etc.). The longitudinal axes of the barrel 26 and the transducer 40 are aligned such that the ultrasonic vibrations are generated in a direction parallel to the longitudinal axis. This transducer orientation allows the size and length of the transducer 40 to be maximized within the barrel 26 while minimizing the obstruction to the airflow. However, as shown with the examples described below, the location and orientation of the transducer 40 may vary to include, for instance, non-axial orientations involving a radial mount.

The styling implement 52 is coupled to the transducer 40 to act as a front end or horn of the vibration assembly 51. In this example, the styling implement 52 is configured as a comb-like attachment that can be detachably secured to the hair dryer 20 via a threaded bolt or other male mating element 56 of the transducer 40. The threaded bolt 56 projects forward to a point that reaches the air outlet 32. In some cases, the threaded bolt 56 may pass through a screen or other covering (not shown) that defines the air outlet 32. To install the styling implement 52, a female mating component or other receiver 58 (e.g., an annular collar) on the styling implement 52 engages the threaded bolt 56 with matching internal threading to position a hair-contacting structure 60 forward of the air outlet 32 as shown. In this case, the structure 60 has a plurality of tapered comb fingers shaped as tines (or teeth) 62 that project perpendicularly outward from a base 64. In operation, the ultrasonic vibrations generated by the transducer 40 propagate axially forward through the threaded post 56, the receiver 58, the base 64, and the tines 62 to reach the hair being styled. The tines 62 are sized and shaped for contacting the hair to be styled during normal use of the hair dryer 20. In this exemplary case, the styling implement 52 has four tines 62 arranged linearly in a single row. However, the arrangement may vary considerably in practice with, for instance, multiple rows or non-linear configurations.

FIG. 2 shows the ultrasonic vibration assembly 51 in greater detail. The receiver 58 in this example includes a central threaded inset 66 having a hole in which the bolt 56 is received. The inset 66 may be made of the same material (e.g., aluminum, duraluminum, etc.) as one or more other sections of the horn 70. For example, if the inset 66 is metallic, the internal threads of the inset 66 can mate with metallic threads on the bolt 56 to produce a metal-to-metal threaded coupling. The inset 66 is fixedly inserted into a collar 68 that may act as a length extender, which is, in turn, fixedly attached to the base 64 of the styling implement 52. The length added via the collar 68 spaces the base 64 and the tines 62 sufficiently far from the heating coils 36 to ensure that a user positions the hair dryer 20 appropriately. The added length may also be helpful for ensuring constructive interference along the propagation path of the ultrasonic vibrations, as described below. The collar 68 may also be radially wider than the inset 66 to distribute the ultrasonic vibrations over a greater area for more uniform transmission through the base 64, which may have a number of holes (not shown) to allow air to pass through.

The manner in which the components of the ultrasonic vibration assembly 51 are coupled to one another may vary from the example shown. For instance, the components may be attached via a variety of different connectors, including snap-fit connectors, a bayonet connector, or other conventional couplings for removably connecting two parts together. In still other cases, the ultrasonic vibration assembly 51 may be constructed of non-detachable components, and instead may be coupled to the hair dryer 20 as a unit, in which case the coupling may be detachable or permanent.

The transducer 40 generally includes a front mass or horn section 70, a piezoelectric section 72, and a rear mass or reflector section 74. In this example, these stages of the transducer 40 are arranged axially in the Langevin configuration. The front mass 70 forms a front-end stage with the other horn sections of the assembly 51, including in this example the threaded post 66 and the styling implement 52, that transmit the ultrasonic vibrations generated in the piezoelectric section 72. To that end, the front mass 70 is shaped and otherwise configured for efficient transfer and transmission of the vibrations. In this example, the front mass 70 includes a cylinder stage that extends forward from the piezoelectric section 72 and a tapered section of decreasing diameter that necks down from the diameter of the piezoelectric section 72 to reach the threaded bolt 56. The styling implement 52 may be considered another section of the horn of the transducer 40. The reflector 74 is positioned behind the piezoelectric section 72 as a rear mass or back-end stage of the transducer 40 generally designed to reflect or direct the ultrasonic vibrations in the desired transmission direction through the front end stage (e.g., through the horn sections). The reflector 74 is sized and weighted to that end. For example, a solid cylinder of stainless steel or other dense material may be used as the reflector 74. The reflector 74 is set at a distance about equal to an integer multiple of the wavelength of the vibrations so that wave reflections will be in phase with the waves emanating from the piezoelectric section 72. The mounting posts 54 may be secured to the reflector 74 as shown in FIG. 1 to minimize losses via transmission to the housing 22.

The piezoelectric section 72 is disposed between the front- and back-end stages of the transducer 40. The piezoelectric section 72 includes a set of piezoelectric discs 78 arranged in a stack. Each disc 78 may be made of Lead zirconate titanate (PZT) or other piezoelectric ceramic(s) or other material(s) with the piezoelectric property of changing shape upon the application of an electric field. PZT and other ceramic materials are useful in the hair dryer context due to heat compatibility, as the heating coils 36 (FIG. 1) are conventionally raised to high temperature levels. The piezoelectric discs 78 as well as the transducer 40 are commercially available from Sunnytec Electronics Co. Ltd. (Taiwan). The disc stack is generally configured so that the vibrations generated by the discs 78 are in phase for constructive amplification. In this case, the stack includes four discs 78 stacked axially, or longitudinally, within the housing 22 (FIG. 1), with each disc 78 oriented transversely to the longitudinal axis. Other disc arrangements are possible, but an even number of discs is useful for maintaining a constructive interference scenario for the vibrations. Electrodes 79 are positioned on each side of the discs 78 to apply an excitation or drive signal to each disc 78. The excitation signal may include an AC component with, for instance, a 160 Volt peak-to-peak amplitude. The amplitude may be increased to amplify the strength of the resulting vibrations. Amplitudes as high as 320 V peak-to-peak have been found to be suitable. The number of piezoelectric discs 78 may be increased to accommodate the higher amplitudes. Other characteristics of the excitation signal, including frequency, may be established through pulse density modulation. The frequency (or effective frequency) of the excitation signal generally determines the frequency of the vibrations generated by the transducer 40. As a result, the excitation signal frequency is generally selected in accordance with the desired vibration frequency of the transducer 40. The frequency may also be selected in accordance with a natural resonant frequency of the piezoelectric discs 78, of which there are a number in the ultrasonic frequency range (e.g., 20 kHz to 1 MHz). Nonetheless, good results are obtainable at 40 kHz, 67.5 kHz, and 77.5 kHz.

Positive and negative pairs of the electrodes 79 are reached via U-shaped contacts 80, which generally run along the stack lengthwise before bending radially inward toward the electrodes 79. Each contact 80, in turn, is connected to the wiring 48 (FIG. 1) that leads to the circuit board 38 (FIG. 1). The contacts 80 may be integrally formed with the electrodes 79. More generally, each contact 80 may be configured as a plate having a flat section. In some cases, the flat section of the plate may provide a stable surface for mounting the transducer 40 within the housing 22 (FIG. 1).

The three stages of the transducer 36 are secured to one another by a bolt or other fastener (not shown) that extends axially forward from the reflector 74 through the discs 78 of the piezoelectric stage 72 to reach the sections of the horn 70. To that end, each disc 78 and each electrode 79 may have a hole (not shown) formed in the center thereof to allow the bolt to pass through. The bolt may have a threaded end configured to engage a matching threaded opening (not shown) in the horn section 70. The bolt may be welded or otherwise fixed to the reflector 74 at its other end. In some cases, the bolt may be integrally formed with the reflector 74. During assembly of the transducer 40, the reflector 74 is rotated relative to the horn 70 for tightening or compression of the stages of the transducer 40. To that end, the horn 70 and the reflector 74 may include opposed pairs of flattened sections (not shown) to provide a surface to be engaged by a wrench or other tool.

The transducer 40 has an overall axial length L_(T), a horn section length L_(H), and a reflector length L_(R), as defined in FIG. 2. Generally speaking, these length dimensions may be selected in accordance with the wavelength of the ultrasonic vibrations to maximize the generation and transmission of ultrasonic vibrations through resonance of the transducer 40. To that end, the dimensions L_(T) and L_(H) may be about λ/2 and λ/4 (or effective multiples thereof), respectively, where λ is the wavelength of the ultrasonic vibrations generated by the transducer 40. The reflector length L_(R) may be an integer multiple of the wavelength λ. When these length conditions are met (or approximately met), the transducer 40 may be driven to an oscillation mode having a node (where vibration amplitudes are at or near a minimum) at a rear face 82 of the reflector 74 and an anti-node (where vibration amplitudes are at or near a maximum) at a front face 84 of the horn section 70. Under these conditions, the vibrations generated by the transducer 40 form standing waves within the transducer 40, effectively reflecting from the back-stage reflector 74 and combining in phase with those traveling forward to the horn section 70 to reach the front face 84 at peak strength. In one example, the overall axial length L_(T) is 56 mm and the horn length L_(H) is 17 mm. As described below, in some cases, the dimensions of the transducer 40 may be structurally limited such that exact adherence to the wavelength-driven configuration is impracticable or impossible, in which case the configuration may deviate from the ideal configuration as appropriate.

The styling implement 52 is also sized and configured to maximize transmission of the ultrasonic vibrations to the hair. Certain dimensions of the styling implement 52 may be selected in accordance with the wavelength of the ultrasonic vibrations to minimize losses. For example, the spacing T_(s) between the tines 62 and the length T_(L) of each tine 62 may be selected to minimize attenuation of the vibrations. To that end, the tines 62 are disposed at the anti-nodes (i.e., points of maximum amplitude) of the wave traveling through the implement 52. The determination of these points was based, in part, on the information set forth in U.S. Pat. No. 5,057,182, the entire disclosure of which is hereby incorporated by reference. Approximations were made for the cross section of the base 64 and different coefficients used for the integers used in the calculations for the tine length and spacing. The locations of the tines 62 and the tapered ends of the base 64 are based, in part, on a note in the above-referenced patent. The taper for each tine 62 is configured to enhance or amplify the wave as it travels down the tine 62 and is based, in part, on the paper entitled “Design of Ultrasonic Concentrators” (L. G. Merkulov, Soviet Physics Acoustics Journal, Vol. 3, No. 1, Academy of Sciences of the USSR, Dec. 31, 1956), the entire disclosure of which is also incorporated by reference. In one example in which the implement 52 is made if aluminum and the ultrasonic vibrations have a frequency of 60 kHz, the tine length may be about 1.84 inches, the length of the base may be about 4.41 inches, the tine spacing may be about 0.92 inches, the thickness of the base 64 may be about 0.19 inches, and the width of the base may be about 0.34 inches. However, these dimensions for the comb-shaped implement shown are exemplary in nature, and other embodiments may include differently shaped implements, including, for instance, other hair-contacting tools or instruments, such as a diffuser, concentrator, and a brush.

With the styling implement 52 attached, the horn section length L_(H) and the length of tine length T_(L) may be considered to present an overall horn length for the transducer 40, another dimension that may be configured in accordance with the wavelength of the ultrasonic vibrations to facilitate transmission thereof. To that end, the overall horn length may also be about λ/4 (or an effective multiple thereof). Alternatively or additionally, the tine length T_(L) (or the combined length of the tines and the base) may be selected to be about equal to an integer multiple of the wavelength.

The styling implement 52 may be made from materials having an acoustic impedance that facilitates the transmission of the ultrasonic vibrations to the hair. Impedance selection thus constitutes another way in which losses due to reflection can be minimized. For example, the styling implement 52 may be made of metals such as aluminum and duraluminum. These materials are well suited for use with the ceramic discs 78 of the transducer 40 because the acoustic impedance of the materials is at about a midpoint between the acoustic impedances of PZT and the hair (which, in turn, is essentially equal to the acoustic impedance of water, the primary component of the hair). The use of a material having an acoustic impedance near the midpoint of the range between the two other impedances (of the origin and destination, for instance) has been shown to maximize transmission and minimize reflection. In these cases, the horn section 70 and the bolt 56 may also be made of aluminum or duraluminum so that the sections of the horn have matching impedances. In other cases, only the horn section 70 may be with a material having an acoustic impedance near the midpoint of the range between the two other impedances. The styling implement 52 may then be made of a material having an acoustic impedance about equal to that of water to match the impedance of the hair. Thus, other materials with suitable impedances may be used for the horn sections of the vibration assembly 51. The use of nylon as a material in the horn sections (including the styling implement) may be useful in this regard. Nylon is characterized by a speed of sound very similar to the speed of sound in hair. Thus, other materials with similar characteristics may also be suitable. More generally, materials that transmit sound equal to or better than hair may be useful as materials from which to construct the styling implements or other horn sections.

In operation, the ultrasonic vibrations generated by the transducer 40 pass through the horn section 70 to reach the other horn sections of the vibration assembly 51, including the threaded bolt 56, the receiver 58, and the styling implement 52. The ultrasonic vibrations propagate through the base 64 to each of the tines 62 and ultimately to the moisture in the medulla of the hair in contact with the tines 62. As described below, the configuration, orientation, and location of the transducer 40 may vary from the example shown and still achieve these results. Other variations described below address the characteristics of the styling implement 52. Still other variations include increasing the number of transducers and styling implements to any desired extent.

Turning to FIG. 3, another exemplary hair dryer 90 is shown to provide an example of an alternative location for an ultrasonic transducer 92. In this case, the alternative location is external to a housing 94 of the hair dryer 90, which may be otherwise similar to the hair dryer 20 of the above-described embodiment. Unlike that case, however, none of the components of an ultrasonic vibration assembly 96 are disposed within a barrel 98 of the housing 94. The vibration assembly 96 includes a styling implement 100 configured in a manner that allows the transducer 92 to be mounted thereto. Thus, the transducer 92 and the rest of the styling implement 100 are detachable as a unit from the housing 94. The styling implement 100 in this example has a circumferential tooth arrangement in which a set of peripheral fingers or teeth 102 are arranged along a circular perimeter of an annular base 104 rather than linearly as described above. Each tooth 102 may again be tapered to form pointed ends that facilitate contact with the hair. In this case, the teeth 102 may be shaped in a sawtooth configuration rather than the comb-like arrangement described above. The annular base 104 may be attached to the barrel 98 via a pressure-fit or other connecting arrangement. To that end, a free end 106 of the barrel 98 may have a reduced rim 108 to accept the base 104 when the base 104 engages the barrel 98.

An electrical connection between the hair dryer 90 and the vibration assembly 96 may be established via the coupling of a pair of matching electrical connectors, in this case, a plug 110 and a receptacle 112. In this example, the plug 110 is disposed at the free end 106 of the barrel 98 to project outward from an air outlet defined by the barrel 98, while the receptacle 112 is disposed on the base 104 of the implement 100. Respective wire pairs 114, 116 then couple the electrical connectors to the vibration assembly 96 and control electronics (not shown). The locations, configuration, and other characteristics of the electrical connectors may vary considerably from the example shown. Rotational positioning elements (e.g., keyed features) may be provided to orient the styling implement 100 properly relative to the barrel 98 so that the electrical connectors align. In some cases, the electrical connectors constitute the positioning elements. To that end, the connectors may be disposed within the walls of the barrel 98 and the implement base 104.

The transducer 92 may be mounted within the styling implement 100 in a variety of ways. In this example, the vibration assembly 96 includes a set of spokes 118 that extend radially outward between a horn section of the transducer 92 and an inner wall of the styling implement 100. The spokes 118 may be narrowed into a slat-like shape with the wider dimension oriented axially so as to minimize the obstruction of the airflow through the styling implement 100. The transducer 92 may be configured similarly to the one described above, albeit with the spokes constituting another section of the horn. In operation, the ultrasonic vibrations generated by the piezoelectric discs travel through a horn section similar to the horn section 70 described above before passing into the spokes 118 and, from there, into the base 104 and the teeth 102, to reach the hair in contact therewith. This embodiment allows a user to optionally enable and use the ultrasonic vibrations when needed and then automatically disable the vibrations for standard hair dryer operation via detachment of the styling implement 100.

In some cases, the base 104 and the teeth 102 of the styling implement 100 may be made of nylon. Alternatively or additionally, the styling implement 100 may be made of the other materials described herein as conducive to transmission of the ultrasonic vibrations. Other portions of the styling implement 100 (e.g., the radial spokes 118) may also be made of nylon as desired.

With reference now to FIG. 4, a hair dryer attachment 120 presents an alternative styling implement for use with the above-described hair dryers. The attachment 120, which also may be made of nylon, has an annular base 122 with a portion that extends axially forward while tapering down to a row of blower fingers 124 extending from a front face of the base 122. The blower fingers 122 may be arranged along a diameter of the front face of the base 122. However, the fingers 124 need not be arranged diametrically or in a row. Each blower finger 124 has a set of exhaust apertures 126 arranged along the length thereof. In this case, the exhaust apertures 126 on each finger 124 are disposed linearly to concentrate the airflow exiting the hair dryer in a laminar like flow pattern. The arrangement of the apertures 126 may vary considerably to present other flow patterns, including those generated by circumferentially disposed apertures. The apertures 126 also need not be distributed along the shaft length of each finger 124, but instead may be disposed near a free end of each finger 124. More generally, the exhaust apertures 126 allow air to be blown through the hair being styled as the attachment 120 is run through the user's hair. At the same time, an ultrasonic vibration assembly incorporating the attachment 120 may include one or more transducers generating ultrasonic vibrations to be transmitted to the hair in contact with the fingers 124. The transducer(s) of the assembly may be disposed in the attachment 120 or within the hair dry housing as described above. In either case, the transducers may use radial spokes to distribute the vibrations as described above, or may instead use one of the mounting arrangements described below.

Turning to FIG. 5, yet another styling implement 130 configured for use as an ultrasonic vibration assembly is shown. As with the above-described styling implement attachment, a transducer 132 is carried by the styling implement 130 rather than within the hair dryer housing. In this case, the styling implement 130 is configured to act as a diffuser. To that end, the styling implement 130 has a housing 134 that generally expands radially outward in the direction of the airflow. In the reverse direction, the housing 134 may taper down to a rim 136 that acts as an insert or a collar at a narrow end 138 for coupling with the air outlet of the hair dryer. At a front end 140, the housing 134 has one or more rims 142 that define a perimeter of an outlet surface 144 from which a set of tapered fingers 146 project forward. The outlet surface 144 also includes a set of exhaust apertures 148 distributed in a pattern to allow the airflow to pass through the styling implement 130 in a diffused manner. The fingers 146 and the apertures 148 may be positioned around a central area 150 of the outlet surface 144 under which the transducer 132 is disposed. The transducer 132 is mounted within the housing 134 in contact with the inner wall opposite the outlet surface 144. The transducer 132 is oriented axially as shown, and may use a variety of different mounting structures or arrangements to be held radially stationary in the desired orientation. While the transducer 132 may be disposed in other locations within the styling implement 130, the location shown is useful because the inner wall of the housing 134 may be flattened in the area contacted by the transducer 132 to match the flat front surface of a horn 152 of the transducer 132. In this way, the ultrasonic vibrations propagating through the horn 152 are efficiently transmitted to the outlet surface 144 and, from there, to the fingers 146 and ultimately to the hair in contact therewith.

FIG. 6 shows the ultrasonic transducer 132 in greater detail. The transducer 132 generally includes the horn 152, a piezoelectric section 154, and a reflector 156. In this example, these stages of the transducer 132 are arranged in the Langevin configuration. The horn 152 is generally configured as a front-end stage to transmit the ultrasonic vibrations generated in the piezoelectric section 154. To that end, the horn 152 is shaped and otherwise configured for efficient transfer and transmission of the vibrations. In this example, the horn 152 is shaped as a truncated cone (or frustum) such that a tapered section of increasing diameter extends forward from the piezoelectric section 154. The horn 152 terminates in a front face 158, which may be flat to maximize contact with the inner wall of the styling implement 130 (FIG. 5) or other component of the housing 134 (FIG. 5). The reflector 156 is positioned behind the piezoelectric section 154 as a back-end stage of the transducer 132 generally designed to reflect or direct the ultrasonic vibrations in the desired transmission direction through the front end stage (e.g., through the front face 158 of the horn 152 toward the housing 134). The reflector 156 is sized and weighted to that end. For example, a solid cylinder of stainless steel or other dense material may be used as the reflector 156. The reflector 156 is set at a distance that is an integer multiple of the wavelength of the vibrations so that wave reflections will be in phase with the waves emanating from the piezoelectric section 154.

The piezoelectric section 154 includes a set of piezoelectric discs 160 arranged in a stack. The discs 160 may be configured, arranged, and driven in a manner similar to the example described above.

The three stages of the transducer 132 are secured to one another by a bolt or other fastener 162 that extends axially forward from the reflector 156 through the discs 160 of the piezoelectric stage 154 to reach the horn 152. To that end, each disc 160 and each electrode may have a hole (not shown) formed in the center thereof to allow the bolt 162 to pass through. The bolt 162 may have a threaded end 164 configured to engage a matching threaded opening (not shown) in the horn 152. The bolt 162 may be welded or otherwise fixed to the reflector 156 at its other end. In some cases, the bolt 162 may be integrally formed with the reflector 156. During assembly of the transducer 132, the reflector 156 is rotated relative to the horn 152 for compression of the stages of the transducer 132 as described above. The horn 152 and the reflector 156 include opposed pairs of flattened sections 166, 168, respectively, to allow a wrench or other tool to help tighten the assembly to reach a suitable level of compression.

The transducer 132 has an overall axial length L_(T) and a horn length L_(H), as defined in FIG. 6. These and other dimensions of the transducer 132 and, more generally, the styling implement 130 (FIG. 5), are selected to maximize the generation and transmission of ultrasonic vibrations through resonance and constructive interference. As described above, the dimensions L_(T) and L_(H) may be about λ/2 and λ/4, respectively, where λ is the wavelength of the ultrasonic vibrations generated by the transducer 132. When these length conditions are met (or approximately met), the transducer 132 may be driven to an oscillation mode having a node (where vibration amplitudes are at or near a minimum) at a rear face 170 of the reflector 156 and an anti-node (where vibration amplitudes are at or near a maximum) at the front face 158 of the horn 152. Under these conditions, the vibrations generated by the transducer 132 form standing waves within the transducer 132, effectively reflecting from the back-stage reflector 156 and combining in phase with those traveling forward to the horn 152 to reach the front face 158 at peak strength. In one example, the overall axial length L_(T) is 56 mm and the horn length L_(H) is 17 mm.

Notwithstanding the foregoing, the radial area taken up by the transducer 132 may present challenges for the design and mounting of the transducer 132 and thereby cause a deviation from the ideal λ/4 configuration. For instance, the diameter of the horn 152 may be limited by the interest in having a minimal amount of space on the outlet surface 144 (FIG. 5) devoted to contact with the transducer 132 (rather than additional fingers 146 or additional outlet apertures 148). As a result, the length of the horn 152 may be shorter than the optimal length in order to achieve resonant operation with the other stages of the transducer 132. In one example with a 1.5″ diameter barrel, the horn 152 is shorter than the optimal length to ensure that the horn 152 resonates at the same frequency as the piezoelectric stage. The shorter horn length also helps to maintain a proper mass differential between the reflector and horn stages in the interest of ensuring that the vibrations are directed toward the horn.

With the horn-shaped (or frustoconical) transducer configuration shown in FIGS. 5 and 6, the lengths may be selected for operation at a number of natural resonant frequencies between about 20 kHz and about 1 MHz. In some cases, the piezoelectric discs 160 may be configured such that the operating (i.e., vibration) frequency exceeds about 50 kHz. The vibration frequency for one exemplary embodiment involving the horn-shaped transducer configuration was above about 60 kHz and, in some cases, about 87.5 kHz. The vibration frequency may be selected in accordance with other operational parameters, including power consumption, temperature level, weight, and size. Differences in device geometry and size may result in different resonant frequencies. Thus, the foregoing operational frequencies are exemplary in nature due to the exemplary nature of the transducer 132, which in this case has a front face diameter of 29.5 mm, a disc/reflector diameter 15.04 mm, and a reflector length of 25.44 mm.

During operation, the vibrations generated by the piezoelectric discs 160 travel axially forward to the horn 152. Once at the horn 152, the vibrations travel further forward to transmit energy to the outlet surface 144. From there, the vibrations spread radially to transfer energy to the fingers 146, which may also be dimensioned in accordance with the vibration wavelength as described above. Through these transmission paths, the ultrasonic energy eventually reaches the hair in contact with the styling implement 130. There, the ultrasonic energy is applied to the moisture entrapped in the medulla of the hair.

The transmission of ultrasonic energy improves the styling of the hair by increasing energy transfer to the hair, as well as facilitating heat transfer within the hair, both which lead to accelerated restructuring of hydrogen bonds within the hair. The ultrasonic vibrations generated by the transducers and transmitted by the styling implements described herein cause a higher level of excitation of the hair molecules to be reached. Therefore, the heating resistance of the user's hair is lowered, and less energy needs to be applied via heat from the hair dryer. The ultrasonic vibrations may also result in more uniform distribution of heat along the above-described styling implements. The excitation of the molecules in the implement housing lowers the heat transfer resistance thereof. More effective transmission of heat through the implement housing lowers the possibility of undesirable hot spots along the housing, which could otherwise damage hair. Turning to the effects on the hair itself, the vibrations apply energy to the hydrogen bonds between the water molecules in the medulla of the hair. To style hair, these weak electrochemical bonds are broken so that the molecular bonds can be reformed with the molecules in different positions. The ultrasonic energy supplies part of the total amount of energy required to break the bonds. As a consequence, less energy is required from the heat, which ultimately helps to prevent damage to the hair follicle resulting from the heat. For all of these reasons, the hair can be styled faster, which, in turn, lowers the total amount of heat applied to the hair, thereby reducing the possibility for damage.

FIGS. 7 and 8 depict two alternative vibration assemblies 180, 182 also configured as styling implements, each of which may have housings configured similarly to the diffuser housing described above. The assemblies 180, 182 differ from the above-described example in transducer location. In both of these cases, an ultrasonic transducer 184 is disposed in a perimeter-mounted location along a housing rim 186. With the assembly 180 shown in FIG. 7, the transducer 184 is disposed within the assembly housing and mounted to an inner surface of the rim 186. In contrast, the assembly 182 has the transducer 184 external to the assembly housing and mounted to an outer surface of the rim 186. The transducer 184 may, in turn, be enclosed within a cover 188, which may be integrally formed with a band 190 that secures the cover 188 to the rest of the assembly 182.

The embodiments shown in FIGS. 7 and 8 generally present insufficient space for mounting the above-described transducers radially against the surfaces of the rim 186. Consequently, the transducers 184 are configured with a horn 192 having an adapter 194 that translates the above-described longitudinal, axial vibration into vibration in a lateral direction toward one of the rim surfaces.

The transducer 184 is shown in greater detail in FIG. 9. The horn adapter 194 includes an L- or elbow-shaped head 196 that projects forward from a cylindrical section of the horn 192 adjacent a piezoelectric stage 198. After extending forward (relative to the other transducer stages), the L-shaped head 196 corners to place an outer end 200 in contact with one of the rim surfaces (FIGS. 7 and 8). In operation, the vibration mode causes the head 196 to move radially (as opposed to axially) toward and away from the rim surface. The transducer 184 thus vibrates along a hammer-like motion path.

As with the above-described embodiments, the transducer 184 also includes a reflector stage 202 in compression fit with the piezoelectric stage 198 and the horn stage 192. The reflector and piezoelectric stages 202, 198 may be configured in a manner similar to the examples described above. The horn stage 192 may have a cylindrical section 204 having an inner end 206 adjacent the piezoelectric stage 198 and an outer end 208 adjacent the horn adapter 194. The outer end 208 may have a flat face from which an axially oriented arm 210 of the horn adapter 194 extends forward. The arm 210 may be integrally formed with the cylindrical section 204 to any desired extent or, alternatively, be attached to the cylindrical section 204 via a variety of different attachment techniques (e.g., welding, adhesive, etc.). The arm 210 projects outward until reaching a corner or shoulder 212 of the adapter 194, at which point another arm 214 projects orthogonally from the arm 210. The arms 210, 214 need not be shaped rectilinearly as shown, and may have curved surfaces to match and accommodate the curvature of the rim.

The overall length L_(T) and horn length L_(H) dimensions of the transducer 184 may be selected in accordance with the above-described considerations. The horn length includes the combined length of the cylindrical section 204 and the adapter 194. The length of the reflector stage 202 is noted as L_(R) and may be an integer multiple of the wavelength in the interest of constructive interference (as is the case with the above-described example).

As described above, the transducer 184 may be configured with dimensions offset from the desired lengths in order to ensure that the horn resonates at substantially the same frequency as the ceramic discs of the piezoelectric stage. With the piezoelectric discs driven with a frequency corresponding with the resonant frequency of the transducer, the horn length may be shorter than λ/4. One exemplary transducer has a main body length of 56 mm, a horn length of 28 mm, a disc diameter of 15.04 mm, a cylindrical horn section diameter of 16.25 mm, an adapter (hammer) width of 12 mm, and an adapter (hammer) lateral extension width (or height) of 15 mm.

Operation of the transducer configuration shown in FIG. 9 has been shown to provide a number of optional resonance points between about 20 kHz and about 1 MHz that may be selected as the operating frequency. The transducer has effectively transmitted ultrasonic energy at about 67.5 kHz, about 75 kHz, and about 77.5 kHz.

FIG. 10 depicts yet another alternative Langevin-based transducer configuration that does not rely on a lateral translation of the vibrations via a horn adapter. In this example, a transducer 220 includes a substantially frustoconical horn stage 222 extending forward from piezoelectric and reflector stages 224, 226. The horn stage 222 is generally shaped to form a contact interface with a flat (or substantially flat) surface disposed, for instance, along a rim surface of an assembly housing. As a result, the transducer 220 may be mounted on a flat surface extruded onto the inner surface of the above-described barrels or styling implements. To that end, the horn stage 222 includes a pair of diametrically opposed flat surfaces 228, each of which may have a parabolic outline. The surfaces 228 generally lie in parallel planes for symmetrical transmission of the ultrasonic vibrations.

With reference now to FIG. 11, an exemplary drive circuit 230 for the above-described vibration assemblies. The circuit 230 includes several components configured for controlling the Langevin transducers of the embodiments in FIGS. 5 and 6. More generally, the circuit 230 is configured for generating a transducer drive signal for the transducers described herein. The circuit 230 as shown does not include any components for controlling or powering the heating coils 36 (FIG. 1). However, the drive and heating control circuitry may be integrated to any desired extent. For example, the input control parameters for activation and deactivation, heating levels (e.g., low, medium and high), and ultrasonic operation may be delivered to both the drive and heating control circuitry for integrated operation. The circuit 230 includes an EMI line filter 232, which is optional depending on whether interference on the AC power line leading to the hair dryer is considered a problem. In some cases, such interference or other noise may affect the operation of the circuit 230 to an extent that the drive signal includes harmonic or other undesired frequency components. The operation of the hair dryer may, as a result, become less efficient (e.g., through diversion of power away from the effective frequencies). Alternatively or additionally, the presence of undesired components in the drive signal may lead to vibration at undesired frequencies, such as audible frequencies. In this example, the filtered AC line power is provided to a high voltage AC-to-DC converter 234 and a low voltage AC-to-DC converter 236. The high voltage converter 234 includes a bridge rectifier 238 and capacitor C3 configured to generate a high DC voltage input V_hv suitable for use in generating the drive signal. The low voltage converter 236 includes a bridge rectifier 240 and a voltage regulating network 242 to generate an output suitable for use as a power supply Vcc for the logic devices of the circuit 230. In this case, the network 232 includes a Zener diode D3 to lower the output of the bridge rectifier 240 and a regulator 244 to generate a stable power supply voltage Vcc of 12 Volts. The regulator 244 may include one of the linear regulators commercially available from National Semiconductor Corporation associated with product number LM78L12.

The exemplary drive circuit 230 is configured as a full H-bridge driver circuit. Other control circuits may instead include other self-oscillating, switched power supplies, such as a half bridge driver circuit. Still other alternatives may be based on a driven circuit configuration in which, for instance, a crystal is used to set an operating frequency. In this case, the power supply voltage Vcc is provided to a timer 246 configured and set in a stable mode for use as an oscillator. To that end, the timer 246 is coupled to a resistor R12 to set the frequency and duty cycle parameters. A commercially available timer suitable for use as the timer 246 may be obtained from National Semiconductor Corporation associated with product number LM555. The oscillating output of the timer 126 may be provided to a divider 248 configured to, for instance, reduce the duty cycle by 50%. A full-bridge driver 250 receives the oscillating signal to develop switch control signals for two full-bridge switch circuit pairs 252. In operation, the switch circuit pairs 252 are selectively activated in accordance with the switch control signals to generate an AC output drive signal based on the high DC voltage input V_hv and apply the signal to the ultrasonic transducer to drive the transducer for generation of the ultrasonic vibrations.

One or more of the above-identified integrated circuit chips or circuit components may be coupled to a heat sink. The heat sink(s) help maintain the operating temperatures of the chips and components to levels within a desired operating temperature range. The heat generated by the heating coils 36 (FIG. 1) as well as the heat generated by the operation of the drive circuit 230 itself may lead to temperatures within the housing 22 (FIG. 1) that would otherwise be elevated to undesirable levels. That said, the operation of the oscillator and other AC-related components of the circuit 230 may remain functional despite the heat levels reached during operation. For instance, the operating temperatures may result in a slight shift in the frequency of the drive signal. In some cases, the frequency shift may be inconsequential, while in other cases other parameters can be adjusted to compensate for the shift.

In some cases, one or more circuit elements may be incorporated into the drive circuit 230 to address spurious vibration modes or other undesired vibrations. For example, a potentiometer may be added to prevent undesirable harmonic frequencies of the drive signal frequency from reaching the transducer. Otherwise, the harmonic frequencies may be audible to the operator of the hair dryer or the operator's pets. The potentiometer may be configured to modify the duty cycle of the oscillator output.

The drive signal generated by the circuit 230 may have a peak-to-peak amplitude of about 160 Volts. When the full H-bridge driver is used, the amplitude may be increased to as high as 320 Volts, in which case the number of piezoelectric discs may be increased accordingly to accommodate the higher amplitude. Thus, the amplitude may fall within the range of about 160 Volts to about 320 Volts for some embodiments. With these amplitudes, the drive signal may, for instance, provide 10-100 Watts of power to the ultrasonic transducer. The amplitudes may exceed that range in some cases (e.g., transformer-based circuits) to deliver more energy to the hair and the styling implement, although at the cost of increased component size and weight.

The drive circuit 230 does not include a transformer to generate the high AC drive voltage, despite the prevalence of transformers in ultrasonic drive circuits. A transformer would add significant and undesirable amounts of size and weight to the hairstyling device. While the non-transformer drive circuit described above may be limited to lower drive voltage amplitudes, that factor can be offset by the selection of the drive frequency and optimal tuning of the transducer horn. For example, the transducer geometry may be adjusted and analyzed to operate at a natural resonant frequency of the transducer. An FEA package was used to analyze and determine the natural resonant frequencies. Geometric adjustments then led to an operational frequency close to the natural resonant frequency of the transducer and the drive frequency of the piezoelectric discs. The mounting of the transducer may also lead to improved transfer of the axial horn vibrations to the barrel. Notwithstanding the foregoing, all component values shown in FIG. 11 are exemplary in nature in multiple respects, including, for instance, that the component values are directed to generating a drive signal with a frequency of 40 kHz.

With reference now to FIG. 12, an alternative drive circuit 260 is configured for controlling the above-described transducers, and has been tested with the transducer shown in the embodiments of FIGS. 7-9. The drive circuit 260 has several features in common with the drive circuit described above and may, in fact, be used to control the other transducers described herein. The drive circuit 260 is also generally configured as a full H-bridge driver, albeit with different circuit elements. For instance, the circuit 260 includes a bridge rectifier 262 to develop the high DC voltage from which the drive signal is generated. An output of the bridge rectifier is also delivered to an AC-to-DC converter 264 for generation of a 15 Volt power supply, which, in turn, is fed to a regulator 266 that develops a 5 Volt power supply used by an oscillator 268 and an inverter 270. The oscillator 268 establishes the frequency of the drive signal by passing its oscillating output to a pair of full-bridge drivers 272, either directly or indirectly through the inverter 270. Each driver 272 then sends switch control signals in accordance with the oscillator frequency to a pair of switch circuits 274, the terminals of which are connected across the transducer discs in the full H-bridge configuration.

FIG. 13 graphically depicts the results of an experiment that shows the increase in energy transmission arising from the application of ultrasonic vibrations. A hair dryer equipped with an ultrasonic transducer removed an additional 12% of moisture from a wet cloth relative to the hair dryer alone. Specifically, the wet cloth was dried with the hair dryer on high air speed for 15 minutes, first with the ultrasonic transducer turned on and in contact with the wet cloth, and then with it turned off. In each case, the cloth was then weighed to determine how much water has been removed. The same hair dryer was used in each case so that thermal masses, maximum temperatures, and other variables remained constant.

Actual testing on hair has shown the improvement to be higher than the results with the wet cloth, but the improvement has not yet been fully quantified. The use of the above-described styling implements generally produce similar moisture removal because the ultrasonic vibrations are transmitted through the solid material(s) of the styling implement directly to the hair in contact therewith.

The use of the disclosed hair dryers with the above-described styling implements is not limited to circumstances in which the styling implement is in contact with the hair being styled. Indeed, the hair need not be in direct contact with the styling implement for the ultrasonic vibrations for improved drying. Less vibration energy reaches the hair, as attenuation of the vibrations occurs during propagation through the air. However, the styling implements help to minimize the gap between the solid horn structures and the hair, thereby minimizing losses. The styling implements also help the user avoid placement of the air outlet too close to the hair or scalp, which may otherwise occur if the ultrasonic vibrations were instead emitted into the air from the barrel. The styling implements may also help to direct or steer the energy from the transducer toward the hair. An ultrasonic transducer vibrating the barrel of the hair dryer may direct a substantial fraction of its energy radially outward rather than forward in the direction of the airflow.

Generally speaking, the material(s) from which the transducer horns (including any attachments) described above are made are selected to ensure effective transmission of the ultrasonic vibrations through the interfaces between the horn and other components. Effective transmission generally avoids reflection or other losses at the interface, which may occur in situations where the impedance of the materials on either side of the interface do not sufficiently match. Suitable materials for the transmission of ultrasonic vibrations in the context of hairstyling devices include aluminum and duraluminum because the acoustic impedance of these materials is approximately halfway between (i.e., at a midpoint between) the acoustic impedances of the ceramic (PZT) discs (45 MRay) and the water in the hair being styled (1.5 MRay), i.e., the final medium. Aluminum and duraluminum, for instance, have acoustic impedances of 17.3 MRay and 17.6 MRay, respectively. Duraluminum may be preferable over aluminum because it is harder. Other materials may be used, including those that have crystalline or polycrystalline material structures. Other materials that are good conductors of ultrasonic vibrations may also be used in one or more of the horn sections, including nylon, brass, and santoprene.

Notwithstanding the advantages of the foregoing examples, the transducer may be mounted in a variety of locations on the hairstyling devices. The transducers also need not be oriented axially, i.e., along the longitudinal axis of a barrel. Even when the transducer is oriented axially, the horn may be configured to transmit vibrations in a direction transverse to the longitudinal axis of the barrel. Thus, the vibrations may be transmitted through the barrel or other housing structure radially, longitudinally, laterally, or any combination thereof. A variety of other translation sections other than the elbow-shaped adapter described above may be used to change the direction of the vibrations. Each housing, styling implement, or other vibrating surface may contain or have more than one transducer associated therewith.

Other ultrasonic generators may be used. As described above, the device responsible for generating the ultrasonic vibrations may be located at various positions, including those within the barrel, handle, styling implement, or other housing component, as well as those exterior to, but in contact with, such structures.

The ultrasonic transducers described above may be secured within the hair dryer housings and implements via an adhesive layer or film. A variety of adhesive materials are well suited for the mounting, including, for instance, those products commercially available from 3M Corporation, which may, for instance, be applied to the inner surface(s) of the barrel. The 3M adhesive products may be configured as a pressure-sensitive film. The adhesive material is generally insensitive to the elevated heat levels within the barrel. The material from 3M Corporation is rated for use at up to 550 F degrees. The adhesive layer generally addresses the challenge of securing the transducers without dampening or otherwise interfering with the transmission of the ultrasonic vibrations. To that end, the adhesive layer may be configured and applied as a thin film. In some cases, the ultrasonic transducers are alternatively or additionally inserted into the barrel or, more generally, the housing or styling implement, in a pressure-fit arrangement. In that way, the ultrasonic vibrations do not experience a potentially lossy barrier to transmission through the interface between the transducer and the styling implement.

The location of the transducers may vary from the examples described above. Still other cases may position one or more transducers within a handle, at a wall or other element separating the handle and another section of the housing, e.g., the barrel, or at any other location within the housing. However, as described above, the transducer locations are not limited to those within the housing, and may be disposed at a variety of locations external to the housing in connection with various detachable styling implements.

A variety of horn shapes may be used with the disclosed hairstyling devices. The transducer horns are not limited to cylindrical or frustoconical shapes. In this way, the disclosed hairstyling devices may accommodate a wide range of barrel and attachment designs presenting vastly different diameters and geometries. The disclosed hairstyling devices are also not limited to Langevin transducers or bolt-clamped transducer stacks. A variety of different piezoelectric arrangements may be used, such that the configuration and construction of the sections, stages, or components may vary from the examples shown above.

Although described above in connection with a number of conventional hair dryer features, the disclosed hair dryers need not include heating coils or other heating elements. In some cases, the energy transmitted by the ultrasonic vibrations may be sufficient to dry and style the hair with the airflow alone (i.e., an unheated airflow).

Although certain hair dryers have been described herein in accordance with the teachings of the present disclosure, the scope of coverage of this disclosure is not limited thereto. On the contrary, all embodiments of the teachings of the disclosure that fairly fall within the scope of permissible equivalents are disclosed by implication herein. 

1. A device for drying hair comprising: a housing having an air inlet and an air outlet spaced from the air inlet to define an airflow path through the housing; a fan disposed within the housing along the airflow path; a hairstyling implement disposed at the air outlet; and an ultrasonic transducer configured to generate ultrasonic vibrations and coupled to the hairstyling implement to transmit the ultrasonic vibrations to the hair.
 2. The device of claim 1, wherein the ultrasonic transducer is disposed within the housing.
 3. The device of claim 1, wherein the ultrasonic transducer is disposed within the hairstyling implement.
 4. The device of claim 1, wherein the hairstyling implement is detachably coupled to the housing.
 5. The device of claim 1, wherein the hairstyling implement is configured as a diffuser.
 6. The device of claim 1, wherein the hairstyling implement includes a plurality of tines.
 7. The device of claim 6, wherein adjacent tines of the plurality of tines are spaced from one another in accordance with a wavelength of the ultrasonic vibrations.
 8. The device of claim 6, wherein each tine of the plurality of tines has a length in accordance with a wavelength of the ultrasonic vibrations.
 9. The device of claim 1, wherein the hairstyling implement has a length of about an integer multiple of a wavelength of the ultrasonic vibrations.
 10. The device of claim 1, wherein the ultrasonic transducer includes a piezoelectric material to generate the ultrasonic vibrations, and wherein the hairstyling implement is made of a material having an acoustic impedance at about a midpoint between an acoustic impedance of the piezoelectric material and an acoustic impedance of the hair.
 11. A device for drying hair comprising: a housing having an air inlet and an air outlet spaced from the air inlet to define an airflow path through the housing; a fan disposed within the housing along the airflow path; and an ultrasonic vibration assembly including a first component comprising a piezoelectric material to generate ultrasonic vibrations and further including a second component coupled to the first component and disposed at the air outlet; wherein the second component comprises a horn material having an acoustic impedance at about a midpoint between an acoustic impedance of the piezoelectric material and an acoustic impedance of the hair to transmit the ultrasonic vibrations to the hair.
 12. The device of claim 11, wherein the second component is configured as a hairstyling implement.
 13. The device of claim 11, further comprising a third component coupled to the first component by the second component, the third component being configured as a hairstyling implement.
 14. The device of claim 13, wherein the third component is made of a material having an acoustic impedance about equal to the acoustic impedance of the hair.
 15. The device of claim 13, wherein the second and third components are constructed of a common material.
 16. The device of claim 11, wherein the first component is disposed within the housing.
 17. The device of claim 11, wherein the first component is disposed within the second component.
 18. The device of claim 11, wherein the second component is detachably coupled to the housing.
 19. The device of claim 11, wherein the second component is configured as a diffuser.
 20. The device of claim 11, wherein the second component includes a plurality of tines.
 21. The device of claim 20, wherein adjacent tines of the plurality of tines are spaced from one another in accordance with a wavelength of the ultrasonic vibrations.
 22. The device of claim 20, wherein each tine of the plurality of tines has a length in accordance with a wavelength of the ultrasonic vibrations.
 23. The device of claim 11, wherein the second component has a length of about an integer multiple of a wavelength of the ultrasonic vibrations. 